Uddin W, Stevenson K L, Pardo-Schultheiss R A
Department of Plant Pathology, University of Georgia, Athens 30602.
Systematic Botany and Mycology Laboratory, USDA/ARS, B011A BARC-West, Beltsville, MD 20705.
Plant Dis. 1997 Sep;81(9):983-989. doi: 10.1094/PDIS.1997.81.9.983.
A species of Phomopsis was isolated consistently from blighted shoots of peach trees in Georgia and Alabama. Isolates of the fungus caused characteristic cankers on current season's shoots of Babygold-7 peach trees when wounded or nonwounded dormant buds, breaking buds, and natural or artificially-created leaf scars were inoculated with conidia of the fungus. Mean canker length for the isolates was 35 mm 30 days after inoculation. No disease developed on control trees. There was no significant difference between the canker length on inoculated wounded dormant buds (59 mm) and nonwounded breaking buds (54 mm). However, cankers from both sites of inoculation were significantly longer than those resulting from inoculated artificially-created leaf scars (33 mm), natural leaf scars (33 mm), and non-wounded dormant buds (30 mm). There was no significant difference in virulence among the 5 isolates of Phomopsis sp. tested, and multi-locus DNA fingerprint analysis resulted in a similarity coefficient of 0.94 among the isolates. Additionally, results of the internal transcribed spacer (ITS) regions sequence comparisons for the isolates were consistent with the multi-locus polymerase chain reaction profiles, and the nucleotide sequences of the ITS region were identical for all 5 isolates. This is the first documentation of the pathogenicity of a Phomopsis sp. associated with shoot blight of peach in Georgia. Rapid development of disease in breaking buds indicates that they may be the primary site of invasion by the fungus. Natural leaf scars and dormant buds may also serve as possible infection courts.
在佐治亚州和阿拉巴马州，一种拟茎点霉属真菌一直从桃树的枯萎嫩梢中分离得到。当用该真菌的分生孢子接种受伤或未受伤的休眠芽、破芽以及自然或人工造成的叶痕时，该真菌的分离株会在“金宝宝7号”桃树当年生嫩梢上引发典型的溃疡病。接种30天后，分离株引发的溃疡病平均长度为35毫米。对照树未发病。接种受伤休眠芽（59毫米）和未受伤破芽（54毫米）后的溃疡病长度之间没有显著差异。然而，这两个接种部位产生的溃疡病都明显长于接种人工造成的叶痕（33毫米）、自然叶痕（33毫米）和未受伤休眠芽（30毫米）后产生的溃疡病。所测试的5个拟茎点霉分离株的毒力没有显著差异，多位点DNA指纹分析得出分离株之间的相似系数为0.94。此外，分离株的内部转录间隔区（ITS）序列比较结果与多位点聚合酶链反应图谱一致，所有5个分离株的ITS区域核苷酸序列相同。这是佐治亚州首次记录与桃树嫩梢枯萎病相关的拟茎点霉的致病性。破芽中病害的快速发展表明它们可能是该真菌入侵的主要部位。自然叶痕和休眠芽也可能是可能的侵染位点。
